Future fuel scarcity issue has become major concern for many energy security policies. As a very potential process to produce fuel, Fischer-Tropsch synthesis (FTS) with cobalt-based catalyst has been developed to produce wax as feedstock for further catalytic cracking. Therefore, this research was conducted to observe Co/Al₂O₃ catalyst properties enhancement through support pretreatment using NH₄NO₃ and Cu promoter addition toward higher activity and selectivity. Catalysts were prepared by dry impregnation method. XRD, BET and TPR analyses were performed to characterize catalysts properties. Activity tests showed CO conversion, H₂ conversion and selectivity of C₅₊ were in the range of 25.1% to 96.2%, 24.2% to 83.7% and 53.5% to 75.9% respectively. Crystallography measurements exhibited 8.6-9.8 nm cobalt particles size. In this study, FTS was evaluated by using fixed-bed reactor at 20 bar, 250 C, and WHSV of 1500 ml/g.cat/h^-1. Support pretreatment increased the pore size of γ-Al₂O₃ and slightly enlarged cobalt diameter. While addition of Cu improved the reducibility of the catalyst.

Conclusion

Addition of Cu promoter on the modified Co-based catalyst can improve the reducibility and activity of catalyst. The Co-Cu(0.6) catalyst obtained from our experiments is the best catalyst that offers higher CO conversion and C₅₊ selectivity. The larger pore size of the support affects the size of the cobalt particles formed. The particle size of Co then affects conversion and selectivity. High conversion values ​​and selectivity of C₅₊ formation are obtained at a minimum Co particle size of 8 nm.