Deactivation behavior of Co-Ru/γ-Al2O3 Fischer-Tropsch synthesis catalyst along the catalytic bed

Deactivation of Ru-Co/γ-Al2O3 Fischer-Tropsch (FT) synthesis catalyst along the catalytic bed is investigated. Catalytic bed was divided into four parts and catalyst morphology changes were studied using BET, ICP, XRD, TPR, Carbon determination, H2 chemisorption and oxygen titration techniques. During the first 200 h, catalyst deactivation was rapid, zero order to %conversion and dependent on the size of active sites. When time exceeded 200 h the deactivation can be simulated with a power law expression: -dXCO/dt=kXCO 28.5. The skeleton of the catalyst charged in 1st half of the reactor did not change significantly. Interaction of cobalt with alumina and formation of mixed oxides of the form xCoO.yAl2O3 and CoAl2O4 was increased along the catalytic bed. Percentage reducibility for the catalyst in the beds 1 to 4 decreased by 2.4, 3.6, 13 and 25.5% and percentage dispersion decreased by 0.5, 1.7, 2.8 and 8.8% for the catalyst in the beds 1 to 4 respectively. Particle diameter increased by 0.8, 1.3, 2.8 and 6.1% for the catalyst in the beds 1 to 4 respectively suggesting higher rate of sintering at last catalytic bed. The amount of coke formation in the 4th catalytic bed was 6 times more than that of in bed 1.

Keywords:

Fischer-Tropsch , Cobalt catalyst , Fixed-bed , Deactivation. Morphology change