CO/CO₂ hydrogenation for the production of lighter hydrocarbons over SAPO-34 modified hybrid FTS catalysts

Fischer-Tropsch synthesis (FTS) is known as the catalytic reactions which convert syngas (CO + H₂) to value-added hydrocarbon products. GTL (gas to liquid)-FPSO (floating, production, storage, and offloading) process is one of the solutions for the monetization of CO₂ rich natural gas or stranded natural gas in offshore. In this work, for the compact design of the GTL-FPSO process, the hybrid FTS catalyst was designed by the physical mixing of the Co/γ-alumina with the hydrocracking catalyst (γ-alumina and SAPO-34), and also Co/SAPO-34 catalyst was prepared without any γ-alumina. SAPO-34 was synthesized by the hydrothermal procedure, and Co/γ-alumina and Co/SAPO-34 catalysts were prepared by the impregnation method. The relationship of catalytic activity, methane selectivity, and C₅₊ selectivity with the acid sites were studied for hybrid FTS catalyst. It was found that by adding SAPO-34 to Co/γ-alumina catalyst, a lighter fuel can be produced. Also, the effect of CO₂/(CO + CO₂) ratio over the Co/SAPO-34 catalyst on the carbon conversion and product distribution was investigated for the first time. It was found that there is an optimum value for CO₂/(CO + CO₂) ratio in the feed that is around 0.25. At this ratio, the C₅₊ selectivities and carbon conversion are the highest, and the methane selectivity is the lowest. It was considered that the high amount of CO₂ in the feed promotes the hydrocracking and the methanation reaction over Co/SAPO-34 catalyst.