Nickel Promoted Cobalt Fischer-Tropsch Catalysts - Effect of Nickel on reducibility and Cobalt dispersion

摘要

The effect of nickel promotion in cobalt Fischer-Tropsch catalysts towards reducibilityand cobalt dispersion was investigated. A series of catalysts loadedwith 20% Co and 0-10% Ni on gamma-alumina were impregnated by the incipientwetness method and calcinated in two steps: First with Ni, then Co.Reducibility was studied with TPR and compared with data from in-situ XRDand TGA. Particle sizes and dispersion was studied with chemisorption, in-situand ex-situ XRD. Sintering of cobalt particles during reduction and at elevatedtemperatures was also studied with in-situ XRD.Promotion with Ni was shown to decrease the reduction temperature of thefirst reduction step of cobalt oxide, while not influencing the second reductionstep towards metallic Co. Ni promotion was also shown to increase dispersionby inhibiting sintering of Co particles both during the second reduction steptowards metallic Co, and at elevated temperatures.