(624c) Synthesis of Bifunctional FeCo Fischer-Tropsch Catalysts: Acid Functionalization of Support and Impact of Fe:Co Ratio on CO Conversion and C5+ Selectivity

The efficient conversion of syngas (a mixture of CO and H₂) into hydrocarbons via Fischer-Tropsch Synthesis (FTS) is a strategically important process in synthetic fuel production. The optimization of this reaction is of interest, as it constitutes an environmentally conscious and feasible method to produce valuable chemicals and transportation fuels from coal, biomass, and natural gas. The extensive array of its product distribution, including light hydrocarbons (C₁-C₄), middle distillates (C₁₁-C₂₂), and complex chains extending up to C₇₀₊, has pushed research efforts to target selectivity control. Bifunctional catalysts have gained attention for introducing tunability by coupling the formation of heavier hydrocarbon chains via FTS with subsequent hydrocracking and isomerization reactions. This two-step process reduces operational and energy costs associated with multiple-stage operations for FTS. These catalysts typically involve two active sites: a metal active phase for obtaining C₅₊ products by surface polymerization reactions associated with FTS and an acidic site that promotes the formation of lighter hydrocarbons. Titanium dioxide (TiO₂), a commonly used support in FTS catalysts, can be acid-functionalized to induce bifunctional behavior, potentially increasing C₅₊ product selectivity and enhancing performance.

In the current work, bifunctional catalysts are synthesized, and their performance for FTS is elucidated by assessing their product distribution. TiO₂­ is selected as the support, which is acid-functionalized with sulfuric acid and optimized via calcination. These catalytic systems are characterized by XRD, XPS, FESEM, EDXS, FT-IR, nitrogen physisorption, and volumetric titration. For the active phases, wetness co-impregnation is used to introduce Fe and Co nanoparticles at different ratios into the functionalized TiO₂, which are known to display favorable CO conversion due to their synergistic effects. By introducing Brønsted and Lewis acid sites into the support architecture and assessing the impact of the Fe:Co ratio, it is hypothesized that these bifunctional bimetallic catalysts enhance FTS performance.