Influence of a Zeolite-Based Cascade Layer on Fischer–Tropsch Fuels Production over Silicon Carbide Supported Cobalt Catalyst

In this work, selective production of middle distillate from synthesis gas was conducted over a cascade catalytic system in a single unit. Co/β-SiC was chosen as an efficient Fischer–Tropsch synthesis (FTS) catalyst (first layer) while proton-type H-ZSM-5 and H-βeta zeolites (second layer) were tested for the subsequent hydroprocessing to produce middle distillate from waxes. Moreover, in order to compare, a prior FTS reference experiment was performed. Catalytic materials were characterized by means of Atomic Absorption, Thermogravimetric analysis, X-Ray diffraction, N₂ adsorption–desorption, Temperature-Programmed Reduction and Temperature-Programmed Desorption. From catalytic results, a distinguishable enhancement of commercial fuels products was observed under the proposed cascade operation compared to the stand-alone configuration or physical mixture. Regardless the zeolite type, FTS over Co/β-SiC with subsequent upgrading was demonstrated to result in the complete elimination of waxes, solving the main weakness of a conventional fixed-bed reactor. Moreover, apart from a selective production of gasoline, the proposed concept provided a significant enhancement of both kerosene and diesel yields, particularly when zeolite H-βeta is incorporated to the cascade system due to its mild acidity and larger pore size.