Effects of calcination and reduction temperature on the performance of Co-Pt-ZrO₂/γ-Al₂O₃ catalysts for Fischer-Tropsch synthesis

Co-Pt-ZrO₂/γ-Al₂O₃ catalysts were prepared by using impregnation method and characterized by BET, XRD and TPR techniques; the effects of calcination and reduction temperature on their catalytic performance for Fischer-Tropsch synthesis (FTS) were investigated in a slurry-phase continuously stirred tank reactor (CSTR). The results showed that the catalysts calcined at high temperature exhibits low activity and selectivity to heavy hydrocarbons, since high temperature calcination may lead a strong interaction between cobalt species and γ-Al₂O₃ support, the formation of less reducible cobalt aluminate species, and aggregation of cobalt oxide crystals. Cobalt oxides cannot be reduced completely at a low temperature, while the aggregation or sintering of the active species may be prominent by carrying out the reduction at extra-high temperature; all these can deteriorate the catalytic performance of Co-Pt-ZrO₂/γ-Al₂O₃. Under 483 K, 2.4 MPa, a H₂/CO molar ratio of 2.0, and a space velocity of 3.6 L/(gcat·h), the catalyst 31.08%Co-0.11%Pt-7.16%ZrO₂/Al₂O₃ calcined at 673 K and reduced in hydrogen at 653 K exhibits high catalytic performance for FTS; the conversion of CO and selectivity to C₅₊ reach 27.0% and 83.0%, respectively.