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

Co-Pt-ZrO2/γ-Al2O3 catalysts were prepared using an impregnation method and characterized by BET, XRD, and TPR techniques. The effects of calcination and reduction temperatures on their catalytic performance for Fischer-Tropsch synthesis (FTS) were investigated in a slurry-phase continuously stirred tank reactor (CSTR). Results showed that the catalysts calcined at high temperatures exhibit low activity and selectivity to heavy hydrocarbons, since high-temperature calcination may lead to a strong interaction between the cobalt species and the γ-Al2O3 support, the formation of less reducible cobalt aluminate species, and the aggregation of cobalt oxide crystals. Cobalt oxides cannot be reduced completely at low temperatures, whereas aggregation or sintering of the active species may be increased by carrying out the reduction at very high temperatures. All these can deteriorate the catalytic performance of Co-Pt-ZrO2/γ-Al2O3. Under the conditions 483 K, 2.4 MPa, an H2/CO molar ratio of 2.0, and a space velocity of 3.6 L/(g-cat/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.