Novel Catalyst Design for Fischer-Tropsch Process

The Fischer-Tropsch synthesis converts syngas, a mixture of CO and H2, into cleaner syn-thetic hydrocarbons. In Canada, converting the flared natural gas into value-added chemicals is environmentally and economically beneficial. The catalyst plays a crucial role in the prod-uct distribution. Although Fe and Co are commonly used catalysts, we selected Fe as the active phase due to its lower cost. Moreover, Fe remains selective at high temperatures. We synthesized Fe-metallosilicates using a novel NHSG method for the first time in the litera-ture and tested them at temperatures ranging from 200°C to 350°C under 20 bar for 90 h. Among four di˙erent Fe-metallosilicates with Ce, Zr, Ti, V metals, the catalytic activity of Fe/Ce/SiO2 and Fe/Zr/SiO2 was the highest with 68 % and 52 % conversion, ,respectively. The NHSG method successfully created a mesoporous catalyst structure. The C7+ selectiv-ity was higher than 60 % at 250 °C. Compared to Co-metallosilicates, the Fe-based catalysts with Zr and Ti catalysts performed better. We then promoted the chosen Fe/Ce/SiO2 and Fe/Zr/SiO2 catalysts with K and Cu metals and observed 20 % higher CO conversion com-pared to their un-promoted counterparts. The methane formation was significantly lower (8 % average) and the C5+ selectivity was higher (up to 60 % at 300°C). Additionally, we synthesized another set of catalysts with Al2O3 (Sasol) supports to assess the impact of NHSG on di˙erent structures. the Fe/Catalox-K,Cu and Fe/Dispal-K,Cu catalysts achieved up to 85 % and 75 %, respectively. Finally, we compared the catalyst activity of Fe/Ce/SiO2-K,Cu , Fe/Zr/SiO2-K,Cu and Fe/Catalox-K,Cu in fixed bed and fluidized bed reactors. Using the same set-up for both reactors allowed us to test under identical conditions — temperatures from 275 °C to 325 °C, flow rates from 100 mL/ min to 200 mL/ min (corresponding to multi-ples of Umf ) and 20 bar pressure, and H2:CO ratio of 2. Overall, catalysts performed better in fixed beds compared to fluidized bed reactors, though at 325°C , the fluidized bed achieved better conversion due to reduced hot spots. The first order reaction kinetic model fits ex-tremely well for all catalysts. Activation energies ranged between 23 kJ mol−1 to 86 kJ mol−1, consistent with the literature. Our hydrodynamic study using residence time distribution (RTD) analysis revealed a plug-flow mixing regime in both reactors, o˙ering flexibility in reactor design and operation.